In the U.S., the command-and-control environmental laws of the early 1970s, together with the ensuing amendments and updates that have been made to them over time,
a) are given considerable credit for cleaner air and water in recent decades.
b) were an inexpensive incentive for industrial polluters to improve performance.
c) were necessary as US industries had zero incentive to control pollution.
d) draws distinction between the needs of firms and costly equipment upgrades.